The present invention pertains to a bladder, having particular usefulness in the sole of a shoe, and a method for making the same.
Bladders have long been used in shoes as a cushion to increase shoe comfort, enhance foot support, reduce the risk of injury and other deleterious effects, and decrease fatigue. In general, the bladders are comprised of elastomeric materials which are shaped to define at least one pressurized pocket or chamber. Typically, a bladder will actually define many chambers arranged in a pattern designed to achieve one or more of the above-stated objectives. The chambers may be pressurized with a number of different mediums, such as air, various gases, water, or other liquids.
Many different chamber configurations have been developed in an effort to achieve the desired results. For instance, bladders have been constructed with a single chamber that extends over the entire area of the sole. One example of this type of bladder is disclosed in U.S. Pat. No. 2,080,469 to Gilbert, entitled xe2x80x9cPneumatic Foot Support.xe2x80x9d Alternatively, bladders have included a number of chambers fluidly interconnected with one another. Examples of these types of bladders are disclosed in U.S. Pat. No. 4,183,156 to Rudy, entitled xe2x80x9cInsole Construction For Articles of Footwear,xe2x80x9d and U.S. Pat. No. 900,867 to Miller, entitled xe2x80x9cCushion for Footwear.xe2x80x9d However, these type of bladder constructions have been known to flatten and xe2x80x9cbottom outxe2x80x9d when they receive high impact pressures, such as experienced in athletic activities. Such failures negate the intended benefits of providing the bladder.
In an effort to overcome this problem, bladders have been developed wherein the chambers are fluidly connected by restricted approaches, however, have not been entirely successful. With respect to the restricted flow bladders. the results have had only limited success in actually providing the desired differences in pressure. Although the independent bladders effectively provide different pressures at various points across the sole, the cost to manufacture the bladders has been prohibitively high. As illustrated in FIGS. 3 and 7 in the ""906 patent to Reed, each independent chamber must be individually pressurized. As can be readily appreciated, this process is not suitable for mass production, particularly in bladders having a significant number of chambers.
The aforementioned problems are overcome in the present invention, wherein a bladder having a unique independent chamber construction can be manufactured without the heretofore high attendant costs.
More specifically, a bladder in accordance with the present invention is particularly useful in the sole of a shoe. The bladder includes a plurality of chambers which are strategically arranged under specific areas of the plantar surface. The chambers are pressurized to a certain internal pressure. Nevertheless, because the chambers define differing volumes of pressurized fluid, each of the chambers are capable of providing a unique resistance. This capacity enables the bladders to provide the desired support and cushion to any particular portion of the foot. Thus, the bladder may be specially adapted to accommodate a particular activity.
In addition, by practicing the method of the present invention, a bladder with these characteristics, can be fabricated quickly, easily, and at a low cost. The method involves selectively forming a number of chambers with an elastomeric material, such that each chamber is in fluid communication with the others. Thereafter, the interior of the product is supplied with an amount of fluid, so that the chambers are all pressurized at the same desired level. The fluid communication is then sealed so that each of the chambers is separated from the other chambers.
As another aspect of the invention, certain portions of the bladder can be pressurized to different levels. In this process, a first set of chambers are formed in fluid communication with each other; and a separate second set of chambers are formed in fluid communication with each other. The first set is not in fluid communication with the second set. These two discrete portions are then each supplied with a quantity of fluid so that each set of chambers is pressurized at a different level. Thereafter, the fluid communications are sealed so that each chamber is separated from the other chambers.
As can be readily appreciated, the practice of either aspect of the inventive process facilitates the manufacture of a bladder having the above-described desirable characteristics in a manner which eliminates the difficulties experienced in the past. Specifically, a bladder having independent chambers that each provide a unique resistance, can be made without having to individually pressurize each chamber. Further, the process is quick, easy, and economical.
These and other objects, advantages, and features of the present invention will be more fully understood and appreciated by reference to the specification and appended drawings.